We have been studying the oncogenic potential of the regulatory serine-threonine kinase CK2, a tetrameric enzyme that is highly evolutionary conserved and overexpressed in many human cancers. In transgenic models, we have shown that CK2alpha produces lymphomas when overexpression is directed to lymphoid cells, and mammary tumors when directed to the mammary gland. CK2-induced tumors exhibit activation of signaling pathways including the Wnt and NF-KB pathways, and we have shown that CK2 is an activator of those and other pro-oncogenic pathways. Here we propose to use homologous recombination and other techniques to elucidate the role of CK2 in Wnt signaling during development and tumorigenesis. We have developed "knockouts" for the two alpha and alpha'catalytic subunits of CK2. CK2alpha'is highly expressed in testis, and CK2alpha'-/- males are infertile. Recently, we have shown that CK2alpha-/- embryos die in mid-gestation. In the next period of this grant, we will focus upon characterizing the defects in the CK2alpha-/- embryos and using them and other tools to elucidate the essential functions of CK2. In the first Specific Aim, we will determine the developmental role of CK2alpha and examine the status of targets of CK2 in the knockout embryos and in MEFs derived from them. In Specific Aim 2, we will determine the role of CK2 in Wnt signaling in cells. In the third Aim, we will cross CK2alpha and CK2alpha'deficient mice to obtain compound knockouts with graded levels of catalytic CK2 expression, and we will engineer mice with a conditional CK2alpha knockout in the mammary gland. These mice will be bred with Wnt pathway oncogene transgenics and treated with carcinogens to determine whether CK2 expression is required for in vivo tumorigenesis;the role of CK2 in in vitro tumorigenesis models will also be assessed. These aims will allow us to fully explore the function of CK2 as a regulator of tumorigenesis and development, in in vivo and in vitro models. Relevance: Kinases have proven to be suitable targets for novel cancer therapeutics. For example, the bcr-abl oncoprotein of chronic myelogenous leukemia is effectively inhibited by Imatinib (Gleevec). Since CK2 is upregulated in all human tumors that have been studied, CK2 may be a suitable target for cancer treatment. Understanding basic CK2 biology and signaling is a necessary prelude to developing novel therapeutics against it.